We study two-body $B$-meson decays to a charmonium state (${\eta }_c$, ${\eta }_c(2S)$ or $h_c$) and a $K^{+}$ or $K^{*0}(892)$ meson using a sample of $349{\mathrm{fb}}^{-1}$ of data collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at the Stanford Linear Accelerator Center. We measure $\mathcal{B}(B^0\to {\eta }_c{K}^{*0})=(5.7\pm 0.6(\mathrm{stat})\pm 0.9(\mathrm{syst}))\times {10}^{-4}$, $\mathcal{B}(B^0\to {\eta }_c(2S)K^{*0})<3.9\times {10}^{-4}$, $\mathcal{B}(B^{+}\to h_c{K}^{+})\times \mathcal{B}(h_c\to {\eta }_c\gamma )<4.8\times {10}^{-5}$ and $\mathcal{B}(B^0\to h_c{K}^{*0})\times \mathcal{B}(h_c\to {\eta }_c\gamma )<2.2\times {10}^{-4}$ at the 90% C.L., and $\mathcal{B}({\eta }_c(2S)\to K\overline{K}\pi )=(1.9\pm 0.4(\mathrm{stat})\pm 1.1(\mathrm{syst}))\%$. We also measure the mass and width of the ${\eta }_c$ meson to be $m({\eta }_c)=(2985.8\pm 1.5(\mathrm{stat})\pm 3.1(\mathrm{syst}))\mathrm{MeV}/c^2$ and $\Gamma ({\eta }_c)=({36.3}_{-3.6}^{+3.7}(\mathrm{stat})\pm 4.4(\mathrm{syst}))\mathrm{MeV}$.

• Received 8 April 2008

DOI:https://doi.org/10.1103/PhysRevD.78.012006